IMPROVED IR THERMOMETER

Abstract: A novel waveguide assembly (30) for use in an IR thermometer of the type used in measuring temperature of the tympanic membrane of the ear for body temperature determinations. The assembly (30) provides a unique arrangement of spacers (20) and a protective sheath (30) to create a durable yet inexpensive waveguide. The spacer (20) includes radially offset contact points (23) that induce moment arms to absorb shock and other forms of rough handling encountered in daily use.

Description: IMPROVED IR THERMOMETER The present invention generally relates to infrared thermometers of the type used to measure body temperature by collecting IR emissions from a patient's tympanic membrane, and more specifically, a novel light wave guide packaging system for higher accuracy and greater durability. BACKGROUND OF THE INVENTION IR thermometers are fast becoming a staple item in health care operations and have revolutionized routine care procedures by eliminating or dramatically reducing the lag time associated with temperature determination in diagnosis. As opposed to prior temperature measuring devices such as conventional mercury thermometers, an IR thermometer is a sophisticated optical - electronic assembly with precision designed and assembled components requiring tightly toleranced and exacting specifica-tions for proper operation. Attention is directed to the teachings of U.S. Patent No. 4,797,840 entitled "Infrared Electronic Thermometer And Method For Measuring Temperature" by Jacob Fraden, for a general description of IR thermometer design and operative characteristics. The teaching of the above-iden-tified patent is incorporated by reference. A critical aspect of IR thermometer operation is the positional arrangement of the wave guide and the sensor inside the body of the device. From a functional standpoint, the wave guide acts to collect the radiation emanating from the tympanic membrane of the patient's ear and accurately guide this radia-tion to the sensor with minimal external influences. The sensor receives the guided radiation and generates a temperature read-ing as characterized by the quantum of radiation sensed. The accuracy of the resulting reading depends in part on the purity of the IR radiation passed to the sensor by the wave guide. The performance of the thermometer will therefore depend in great measure on the design of the wave guide and its relationship with the other components of the thermometer. Another important consideration in system design is the durability of the precisely arranged components. A system that leaves the factory with acutely sensitive settings that are quickly lost within the first few days of use has significantly reduced value to the consumer. Indeed, thermometers that become inaccurate through the normal bumping and shaking encountered in daily use are of limited value regardless of the initial accuracy from the factory. It has, therefore, become a critical aspect of thermometer design to devise an arrangement of opera-tive elements that incorporates a ruggedness and durability sufficient to withstand daily abuse in practice without signifi-cant loss of performance. To attain these objectives, much progress has been made in packaging the electronics and electro-mechanical components to withstand typical daily rigors of use. These are important advancements that allow greater use of the product at less cost and concern about abuse. Notwithstanding this progress, IR thermometers remain prone to loss of fidelity due to normal bumps. This fidelity loss is often traced to the optics dis-cussed above, wherein heavy handed use causes slight but signal disruptive misalignment of the wave guide. Significant mis-alignment of the optics will dramatically curtail the IR thermometers accuracy. It was with this understanding of the problems associated with prior optic system design that led to the present inven-tion. OBJECTS AND SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to provide an apparatus for protecting the positional integrity of an optic system used in conjunction with an IR thermometer. It is another object of the present invention to provide a packaging arrangement that provides shock resistance to optical elements arranged in an IR thermometer. It is a further object of the present invention to provide an arrangement of concentric elements and specifically deline-ated spaces between the elements to create a low impact resist-ant optical instrument. It is yet another object of the present invention to pro-vide a shock resistant wave guide that is economical to manufac-ture and inexpensive to assemble. The above and other objects are realized in a wave guide system that combines precision optics with an external rigid protective sheath. The outer sheath is positioned concentri¬ cally around the wave guide but spaced therefrom, creating a precisely dimensioned gap between the wave guide and the outer sheath. Within this annular gap, a semi-rigid spacer is placed establishing line contact with both the outer sheath and the inner wave guide. The line contact with the inner wave guide is radially offset from the line contact with the outer sheath thus creating a matrix of perpendicular bending moments at regular intervals within the spacing structure. In accordance with the varying aspects of the present invention, a continuous sleeve is positioned in the annular space between the wave guide and the outer sheath, wherein the sleeve has plural tabs extending therefrom, selectively posi-tioned to permit slight deformation in response to external forces, bumps or rough handling. The foregoing features of the present invention may be more fully appreciated in the context of a specific illustrative example thereof presented in conjunction with accompanying draw-ing of which: DESCRIPTION OF THE FIGURES Figure 1 is a perspective view of an illustrative sheathing arrangement in accordance with the present invention; Figure 2A is a cross-sectional view of the embodiment depicted in Figure 1; Figure 2B is a segment view of forces acting on a portion of spacer 20; Figure 3A is a second cross-sectional view of the embodi-ment of Figure 1, under the influence of stress; Figure 3B is a segment view of the spacer of 3A; Figure 4 is a second embodiment, shown in cross-section view; Figure 5A is a third embodiment, shown in perspective view; Figure 5B is a further embodiment; and Figure 6 is a depiction of an extrusion process for making the embodiment of Figure 5A. DESCRIPTION OF THE PRESENT INVENTION The present invention generally provides a shock absorbing spacer to prevent physical distortions and damage to the light transmission medium in light-based analytic instruments such as IR thermometers. The spacer is positioned and configured within an annular gap between the transmission medium and an outer sheath to form a series of contact points that are radially off-set. By positioning the supporting contact points in offset orientation, the impingement of external forces on the trans-mission medium are translated into bending moments along the perimeter of the spacer — thereby dissipating the force without distortion to the transmission medium. Turning now to the Drawing, Fig. 1 depicts the layered arrangement of the transmission medium (wave guide or other, depending on application) , spacer and outer sheath. Specifi¬ cally, a light transmission medium 10 having a generally cylindrical shape is encased by a protective sheath 30 having a generally circular inner diameter that is greater than the outer diameter of the transmission medium forming an annular gap therebetween. The spacer 20 is positioned in a snug fit in this annular gap, wherein the spacer has a cross-sectional shape that departs from both the outer surface of the transmission medium and the inner surface of the protective sheath. In this way, open areas are created between the spacer 20, the protective sheath 30 and the transmission medium. The arrangement of Fig. 1 is depicted in cross-section in Fig. 2A. As shown in cross-section, the spacer 20 is a hexagon accurately held in place between outer sheath 30 and the inner transmission medium 10. This positioning establishes contact points between the spacer and the protective sheath at 23; and between the spacer and transmission medium at 24. With this arrangement, open areas are formed around the perimeter of the transmission medium, e.g., 25 (between the spacer and sheath) and 26 (between the spacer and transmission medium) . The loca-tion of open areas vis-a-vis the points of contact create moment arms along the spacer as depicted in Fig. 2B. It is the moment arms thereby created that act to absorb induced shock to the assembly by partial deflection of the semi-rigid spacer 20. In Fig. 2B, F(t) is the force vector imparted by the transmission medium and F(s) is the counteracting force vector imparted by the sheath. Representative dimensions for the components depend on the actual implementation of the system. For use in a IR thermom-eter, the transmission medium will typically have a diameter of 0.123/0.118 inches. The outer sheath will have an inner diam-eter of approximately 0.158/0.154 inches. Finally, in such an arrangement, the spacer will have an "effective" diameter of 0.140 inches, a thickness of 0.008 inches and is preferably formed by extrusion using polyurethane or nylon. Turning now to Fig. 3A, the arrangement of Fig. 2 is shown, but now undergoing an external force F(l) representing a shock or bump to the assembly. This force acts to distort the outer protective sheath from the circular cross-section to a cross-section of generally elliptical shape. The application of this force is, however, not translated to the inner transmission medium. To the contrary, this medium remains circular, as the external force is absorbed by the counter balancing distortion of the spacer, and, particularly, the deflection of the semi-rigid moment arms within the spacer. This can be clearly seen in Fig. 3B depicting a portion of spacer 20 undergoing force induced deflection, via force vectors F(s) and F(t) . Turning now to Fig. 4, a second inventive arrangement is shown, wherein the spacer 20 is completely contiguous with the transmission medium 10, but spaced from the outer sheath by acutely angled tabs 33. In this arrangement, induced forces are absorbed by the deflection of the angled tabs. Although only four tabs 33 are shown, the use of more tabs, distributed around the perimeter of the spacer 20 is contemplated. In Fig. 5A, a further inventive arrangement is shown, one that can be assembled through the use of extrusion techniques. In this arrangement, the spacer has an exterior surface with a star-shaped cross-section and an interior surface shaped to fit snugly over the transmission medium without open areas. In this form, the absorption of forces is accomplished via the flexible and/or compressible nature of the material used to form spacer 20. Alternatively, the spacer may have an interior surface with a cross-section identical to that of its exterior (i.e., star shaped) thereby establishing open areas between the transmission medium 10 and the spacer 20 as depicted in Fig. 5B. In both arrangements of Fig. 5, the outer sheath has a generally cylindrical inner surface. In Fig. 6, an extrusion molding technique for making the foregoing arrangement of Fig. 5A is shown. In this process, the transmission medium 10 is passed through a first die 70 having an opening shaped to correspond to the outer shape of the spacer. Thereafter, the extruded spacer 20 is fitted into a cylindrical sheath, thus forming the open areas between the spacer 20 and the sheath (not shown) . The above descriptions are illustrative of the inventive concepts and many modifications and adaptations thereof will be readily apparent to those skilled in this art without departing from the scope and spirit of the invention.

Claims: What is claimed is; 1. An apparatus for transmitting information in the form of electro-magnetic radiation, comprising: an elongated electro-magnetic radiation propagation means having a substantially uniform outer diameter; a protective sheath means with an inner surface having a shape corresponding to that of said propagation means with an inner diameter greater than the outer diameter of said propaga-tion means and positioned substantially concentric about said propagation means for the full length thereof; a semi-rigid spacer means having a generally uniform cross-section positioned in the annular gap formed between said propagation means and said protective sheath means, wherein said spacer means provides plural line contacts with said protective sheath and plural line contacts with propagation means, wherein said line contacts with said propagation means are off-set from said line contacts with said protective sheath means to create moment arms along the perimeter of said spacer means. 2. The apparatus of claim 1 wherein said spacer means has a polygonal cross-section. 3. The apparatus of claim 2 wherein said polygonal cross- section is a hexagon. 4. The apparatus of claim 3 wherein said hexagon is isometric. 5. The apparatus of claim 1 wherein said propagation means is a fiber optic cable. 6. The apparatus of claim 1 wherein said propagation means is cylindrically shaped. 7. The apparatus of claim 1 wherein said spacer means is star-shaped. 8. In combination in an IR thermometer of the type used to measure the radiation emanating from the tympanic membrane of a patient, the improvement comprising an IR wave guide partially encased in a concentric spacer means which is further partially encased by a protective sheath means wherein said spacer means is characterized by a cross- sectional shape that departs from the cross-sectional shape of said protective sheath or said IR wave guide, whereby a series of axially distributed spaces are positioned between either the spacer means and wave guide or spacer means and protective sheath means or both. 9. The IR thermometer of claim 8 wherein said spacer means is semi-rigid and provides plural line contact between said IR wave guide and said protective sheath. 10. The IR thermometer of claim 9 wherein said line contact is radially offset. 11. The IR thermometer of claim 10 wherein said spacer means has plural moment arms and absorbs externally applied forces by distortion of said moment arms. 12. A method of manufacturing a electro-magnetic radiation transmission apparatus comprising the steps of: passing a radiation transmission medium having a first cross-section shape through an extrusion die having a second cross-section shape wherein said first cross-section shape has a smaller diameter than said second cross-section shape, injecting into an annular gap in said extrusion die a semi-fluid curable compound to form a third cross-sectional shape corresponding to and formed by said second cross- sectional shape and further characterized by a * non-circular cross-section with a plurality of raised elements therefrom. 13. The method of claim 12 wherein said radiation transmission medium is further encased in a concentric protective sheath wherein said annular space between said light transmission medium and protective sheath is partially filled with said extruded curable compound. 14. The method of claim 12, wherein said radiation transmission medium is formed of fiber optic cables. 15. A communication line using electro-magnetic radiation to transmit information, comprising: a wave guide means for passing with minimal distortion electro-magnetic radiation corresponding to information for communication; a protective sheath means for wrapping around said wave guide means forming an annular gap therebetween; a spacer means positioned in said annular gap having a cross-sectional shape departing from the cross-sectional shape of said protective sheath means whereby voids are formed between said spacer means and said sheath means. 16. The communication line of claim 15 wherein forces acting on said sheath means are absorbed by distortion in the shape of said spacer means.

Inventors: MOORADIAN MARK, MOORADIAN, MARK
Applicants: THERMOSCAN INC, THERMOSCAN, INC.
Application year: 1994
Main classification: A61B6
IPC codes: A61B5, G01J5, G01K13